Behaviour of RC beams strengthened with CFRP laminates at elevated temperatures

Petkova, Diana (2010) Behaviour of RC beams strengthened with CFRP laminates at elevated temperatures. (PhD thesis), Kingston University, .

Abstract

Strengthening of existing structures has become an important aspect of civil engineering. Various methods exist and have been developed in the last few decades one of which has become increasingly popular- strengthening using fibre reinforced polymers. Their excellent mechanical properties and resistance to different environmental conditions make them a viable alternative to the traditional materials like concrete and steel. In this study the effect of elevated temperatures on the behaviour of FRP strengthened reinforced concrete beams is investigated. The behaviour of reinforced concrete beams strengthened with FRP laminates has been investigated by different researchers in the last two decades. Ultimate load, failure modes and improved techniques for strengthening have been the main areas of interest. As a result of the extensive research several classifications and design guidelines have been proposed to ensure better performance and prevent premature failures of the systems. One important aspect of the strengthening is the susceptibility of polymers to significant and rapid reduction of their strength when exposed to elevated temperatures and fire. Little research has been done up-to-date on the residual properties of FRP strengthened systems after heating and cooling. Three experiments have been conducted for the purpose of this study. The bond strength of CFRP strengthened systems is first investigated for temperature range of 20[sup]oC to 300[sup]oC. The behaviour of small-scale strengthened beams during the heating process is presented next. The third experiment is then designed to determine the residual flexural capacity of the heated and cooled minibeams. The results are presented and compared indicating residual strength of the systems to 30% compared to their performance at room temperature.

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